By Rod Roller, Central Alabama Miata Society

WARNING: This modification requires the
removal, disassembly, modification, reassembly, and reinstallation of the trunk mounted
lock cylinder. If you are not entirely confident in your ability to do this you should not
attempt it. If performed improperly, you could damage the lock enough to make it
unuseable, requiring you to purchase a new lock cylinder.

To perform this modification you will need several things:

10mm cresent or socket wrench

Pliers, preferably needle-nosed

Screwdriver, narrow flat blade

Dremel Moto-tool, or similar electric tool capable of grinding small
metal parts, with a metal burring bit and a small round stone bit

Protective glasses

Between 1 and 2 hours, depending on your skill

STEP 1: REMOVE LOCK CYLINDER FROM CAR

When you remove the inside trunk panel the back of
the lock is exposed. Twist the plastic clip downwards that holds the connecting rod, then
pull the rod from the lever arm. Now remove the E-clip (using pliers and/or sharp
screwdriver) holding the lever arm and spacers, then remove the arm and spacers and set
them aside. Be sure to remember the order they were in! Two bolts hold the lock in place,
remove them with a 10mm socket. The lock should now be free. Reach up under the rear
bumper and pull the lock cylinder out, but it will require some effort because the bumper
fits tightly against the cylinder.

STEP 2: DISASSEMBLE LOCK CYLINDER

Now that the cylinder is free, you have to
disassemble it. This is the only tricky part, but not too bad. Remove the polished cap
(where the key goes in) using a small(narrow) screwdriver. Pry under the edge of the cap
where the two indentations are to free the cap. The cap will bend somewhat but you should
be able to get it off with out much distortion. The cap can be easily straightened with
needle-nosed pliers once it is removed. The key door assembly will be under the cap, set
the cap and door assembly aside. Now insert the key into the lock tumbler(the center
part). Be sure to hold the key in the tumbler, and slowly remove the tumbler from the
outer casing. IF THE KEY COMES OUT, YOUR LOCK WILL COME APART!!! Set the tumbler/key
combination aside, keeping the key in!

STEP 3: GRIND OFF METAL TAB PREVENTING ROTATION

The danger is now mostly over. Clean any excess
grease out of the lock casing. Examine the tumbler and compare with the photos below to
determine which tab needs to be removed. Use a Dremel or similar tool to grind off the tab
shown in the photos. WEAR EYE PROTECTION WHILE GRINDING!

Be sure not to leave any rough edges, and clean all
metal fragments out of the casing before re-inserting the tumbler. Insert the tumbler with
key still inside and verify that key now turns both directions smoothly. If it seems to be
snagging when turning counter-clockwise remove tumbler/key and verify that all of the tab
was removed. If the key turns smoothly you are ready to put it back together.

STEP 4: REASSEMBLE LOCK CYLINDER

Insert the tumbler COMPLETELY in the casing, and
carefully remove the key leaving the tumbler in the casing. Place the key door assembly
back on top of the cylinder assembly and place the polished cap back on the assembly. Use
pliers to press the sides of the cap down if necessary, ensuring the cap will stay on the
cylinder. Now insert the key and test rotation one more time before reinstalling in car.

STEP 5: INSTALL LOCK CYLINDER INTO CAR

Reinstall lock cylinder in car, reversing removal
steps. It will be difficult to get the cylinder back in place because the bumper is so
close to the car. Keep trying and you will get it eventually. There is a foam padding ring
around the key hole in the bumper, I have found it is helpful to remove and discard this
ring since it tends to interfere with installation of the cylinder. Once cylinder is in
place, replace 10mm bolts. Replace spacers and lever arm on lock shaft in correct order,
and secure with E-clip. Place connecting rod back in hole on lock arm and rotate plastic
clip until rod is locked in place. Replace trunk inner panel.

YOU ARE DONE!

To use the locking feature, the trunk lid must be
closed. Verify the console release still works properly. Now close trunk lid, insert key,
and turn key counter-clockwise. You should hear and feel a small "pop". This is
the console release being disabled. Pull the console release, it should now do nothing.
Place key in trunk lock and turn clockwise, opening trunk. You will propably hear two
"pops", the first is the console release being reactivated, the second is the
trunk latch opening. Close trunk lid and pull console release to verify it now opens
trunk. THAT'S IT!